Effects Of Processed Corns On The Synchronization Of Nitrogen And Energy Release In Rumen And On Small Intestine Digestibility In Lactating Cows

This paper discusses the effects of processed corns on the synchronization of nitrogen and energy release in rumen and on small intestine digestibility in lactating cows. Based on In Vivo, In Sacco and In Vitro, 5 experiments were conducted as follows:In Exp1, corns were processed by physical methods (expanding, pelleting, dry rolling and roasting) and were analyzed with other feedstuffs (including wheat bran, soybean meal, flaxseed meal, hay and corn silage) to determine whether the nutrient contents in processed corns had any changes. The result shows that DM, OM, CP, starch, NDF, Ca and P contents in processed corns have no significant changes compared with that of control corn (Pï¹¥0.05).In Exp 2, three Chinese Holstein lactating cows with permanent ruminal cannulas were used as experimental animals to investigate the regularity of ruminal degradability of processed corns and above-mentioned feedstuffs by nylon bag technique. The result shows that the effective ruminal degradability P values of DM, OM, CP and starch are significantly different among processed corns. Compared with control corn, the effective ruminal degradability P values of expanded and pelleted corns increase significantly (P<0.05 or P<0.01); the P values of roasted corn decrease apparently (P<0.05); while that of dry rolled corn have no significant changes (Pï¹¥0.05). The P values of DM, OM and CP in soybean meal are between expanded and pelleted corns (Pï¹¥0.05); the P values of flaxseed are much alike that of roasted corn (Pï¹¥0.05).In Exp 3, DFCCS-â…¡dual-flow continuous culture system was used to study the ration formulation on the synchronization of nitrogen and energy release. The result shows that based on BCP synthesis, the suitable substrate amounts is 45g/d in each fermenter, the best cultural time is 12h; the ideal substrate combination is expanded corn+soybean meal+flaxseed meal +hay+corn silage among various combinations; the best nitrogen and energy ratios are 37gRDN/kgFOM in early lactation period, and 31gRDN/kgFOM in mid and late lactation period. In addition, pH values, NH3-N and VFA concentrations are changed in different combinations.In Exp 4, BIF was used to investigate the digestibility of non-degradable ruminal residues of processed corns (after 12h culture in rumen) in small intestine. The result shows that DM and starch digestibilities are different among all processed corns residues. DM and starch digestibilities of expanded corn are significantly higher than that of other groups in small intestine (P<0.05), while no apparently differences are found among other groups (Pï¹¥0.05).In the last experiment, 16 cows in early and midlaction period were selected to conduct a 50 d feeding experiment with four diets (expanded corn, pelleted corn, roasted corn and control corn). The result shows that the average milk yielding per cow has no significant changes when fed the four diets (Pï¹¥0.05). The higher synchronized diets (expanded corn, pelleted corn) do not significantly increase milk production, which is out of expectation; the lower synchronized diet (roasted corn) has the tendency to decrease milk production, but is insignificant (Pï¹¥0.05). Compared with control group, the milk fat, protein, lactose percentages and total solids in other groups have no apparent differences (Pï¹¥0.05), but the fat percentage in the lower synchronized diet is higher than that of the higher synchronized diet (P<0.05), which is consistent with expectation.